    [Reference] Korean Patent No. 10-1022561 filed Mar. 8 20110.
In general, when a vehicle collides with another vehicle or an object, bumpers consisting of a bumper face and a shock absorbing foam installed on the front and rear surfaces of the vehicle absorb and buffer the shock being delivered thereto at the time of collision thereby reducing the damage on the vehicle as well as protecting passengers in the vehicle.
That is, as the bumper face is being pushed toward the vehicle body and the shock absorbing foam is pressed between the vehicle body and the bumper face, the shock due to the collision is being absorbed and buffered.
The above type of a bumper can fully serve its intended function when the vehicle collision occurs at a relatively low driving speed. However, when the collision occurs while the vehicle is driven at a speed of over 30˜40 Km/h there is a limitation on the buffering capacity of the shock absorbing foam and the bumper face, and the shock absorbing foam are easily destroyed by the collision shock thus raising a problem.
To solve the above-mentioned problem, a vehicle bumper utilizing a magnetic force due to two permanent magnets with an equal polarity installed at regular intervals has been proposed. In other words, the collision shock on the bumper is absorbed by the repulsive force between the two permanent magnets with the same polarity.
Accordingly, when the vehicle collision occurs while the vehicle is driven at a speed of over 30˜40 Km/h there will be an added shock buffering capacity provided to the vehicle due to the repulsive force between the two permanent magnets, which enables to protect and restore the shock absorbing foam to its original shape, which might have been pressed toward the vehicle at the time of collision as the bumper face is being destroyed by the collision shock.
However, the above vehicle bumper employing the magnetic power has also limitation in its shock absorbing capacity when the collision occurs while the vehicle is driven at a speed of over 60 km/h, when the vehicle body including both the bumper face and the shock absorbing foam will be seriously damaged and passenger in the vehicle cannot be protected from serious damage.
As an alternative, the inventors of the present invention previously filed an application regarding an improved vehicle bumper provided with a permanent magnet and an electromagnet, which can effectively buffer a collision shock thereby preventing vehicle damage as well as passengers in the vehicle regardless of the vehicle speed at the time of the collision, and was granted in Korea, wherein a shock absorber of a vehicle using permanent magnets and electromagnets, including a first permanent magnet installed on the internal surface of the bumper face; a second permanent magnet which is installed on the front surface of a shock absorbing foam, installed on the front surface of the vehicle body, and has the same polarity as that of the first permanent magnet; and an electromagnet which is installed on the internal surface of the shock absorbing foam, and has the same polarity as that of the second permanent magnet thereby enabling to absorb a collision shock due to the strong repulsive force provided between the permanent magnet and the electromagnet even when the vehicle operating speed exceeds 60 km/h.
However, the above patent has problems that because the bumper face and the permanent magnet installed in a vehicle are formed as a single unit, respectively, they can be easily damaged in their entirety or malformed by the collision shock and because they are exposed to the outside of a vehicle they are vulnerable to oxidation process resulting in corrosion and their magnetic power also deteriorate according to time passage thus not functioning properly.